Processes for depositing a thin film layer on a substrate are known in the art. An example of one such process is physical vapor deposition (PVD). Inherent in the PVD process is the formation of surface protrusions on the thin film during deposition of the material forming the thin film. These surface protrusions can be many times the size of components to be later deposited on the thin film. As a result, the surface protrusions may project into layers of material formed on the thin film layer. In such cases, the surface protrusions may result in an unwanted short circuit between the thin film layer and a layer formed on top of the thin film layer. For example, in the baseplate of a field emission display (FED), such surface protrusions could result in a short circuit between the thin film layer on which emitters are formed and an extraction grid positioned above the emitters. This is true because a surface protrusion can have a height which is much greater than the height of an insulating layer positioned between the thin film layer and the extraction grid.
Various techniques have been attempted in the prior art in an effort to alleviate the adverse effects of surface protrusions. First, the parameters of the PVD process have been adjusted to try and prevent formation of the surface protrusions. This technique has not been entirely successful in that some surface protrusions are inherently formed during the PVD process. Given that some surface protrusions are formed, chemical-mechanical planarization (CMP) has been utilized to try and remove these protrusions from the thin film layer. When CMP is used directly on the thin film layer, however, the larger surface protrusions sometimes break lose and scratch the surface of the thin film layer. These scratches can result in unacceptably large areas of the thin film being unsuitable for the formation of the desired components.
In view of the problems associated with these processes for removing surface protrusions from a thin film, it is desirable to develop a process which removes the surface protrusions from the thin film without detrimentally affecting the surface of the thin film layer.